RationaleWith the intention to reduce the invasiveness of the retropubic and trans-obturator approach, the MiniArc was developed. It consists of a shorter polypropylene mesh tape that is inserted into the trans-obturator direction using self fixating arms. The first reports about the outcome of this innovative surgical technique are very promising, the system is easy to handle and causes limited tissue damage. Theoretically, the MiniArc is less painful and safer as compared to retropubic or trans-obturator approach as it avoids the retropubic space, does not pass through the obturator muscles and does not reach the area of the obturator vessels. Cadaver studies have shown that the pull-out forces of MiniArc are far higher than will be realized in living subjects. Theoretically, the MiniArc is as effective as retropubic and trans-obturator meshes as the location of the tape during these procedures is identical. However, this statement has to be proven in a prospective randomized controlled trial.

If MiniArc would prove to be equally efficient as a Monarc transobturator subfascial hammock and it would also be less morbid (including post-operative pain), the MiniArc could be the most cost-effective strategy to deal with SUI that is available at the moment. We propose a multi-centre randomised controlled trial comparing efficacy and morbidity of MiniArc and transobturator Monarc.

Objective

To investigate the hypothesis that MiniArc is non-inferior in effectiveness compared to Monarc in the management of stress-incontinence. We further hypothesize that there are differences in morbidity and post-operative recovery between both procedures as MiniArc is a less invasive technique. We will evaluate the effects and costs of both interventions. Therefore we compare MiniArc and Monarc for:

efficacy as surgical correction of stress-incontinence

post-operative pain

complications

morbidity and post-operative recovery

the need for repeated stress-incontinence surgery or specialized physiotherapy

pelvic floor function

cost-effectiveness from a societal perspective

Study populationPatients who have a scheduled surgery for symptomatic stress urinary incontinence (SUI).

Patients who have stage 2 or more genital prolapse (according to the ICS classification) are excluded. Patients who undergo surgery for recurrence of stress-incontinence are excluded as are patients who undergo concomitant surgical procedures. Patients with a BMI > 35 kg/m2 are also excluded.

InterventionAfter patients are assigned to a surgical treatment through balanced non-restricted randomization, they undergo a MiniArc or Monarc procedure. All procedures will be performed under general anesthesia, under spinal analgesia or under a combination of local analgesia whilst strictly adhering to the insertion guidelines of both needle procedures.

Outcome measures

Subjective cure and pain are considered as primary outcomes. Objective cure, morbidity, duration of catheter use, disease and domain specific quality of life, general specific quality of life, performed interventions, and costs in the first year after stress incontinence surgery are considered as secondary outcomes.

Power/data analysis

We hypothesize that MiniArc is at least as efficacious as Monarc based on subjective cure. We assume that 90% of patients treated with Monarc indicate being cured at 12 months post intervention. The MiniArc procedure is considered inferior to the Monarc procedure, if the percentage of patients treated with MiniArc who indicated being cured drops below 75%. To achieve 90% power to detect a non-inferiority margin difference of minus 15% between the MiniArc and Monarc groups, sample sizes of 85 in each group or 170 in total are needed. The test statistic used will be the one-sided Z test (pooled). The significance level of the test was targeted at 0.025.

At the same time we hypothesize that the MiniArc procedure is superior to the Monarc procedure regarding pain, because it is a less invasive procedure. Based on prospective documentation of pain scores we know that patients undergoing trans-obturator mid-urethral sling procedures score on average 40 (standard deviation = 16) on a 0 to 100 VAS score assessing pain at the first evening after surgery. We consider a difference of pain score of 20% as clinically relevant. We further assume that the most reliable estimate of a patientís pain level after surgery is derived by averaging her pain scores on the first three days after the intervention. With a power of 90% and a significance level of 0.05 using a two-sided two-sample t-test, the sample size necessary to detect a difference of 8 between the null hypothesis that both groups means are 40 and the alternative hypothesis that the mean in the MiniArc group is 32 with estimated group standard deviations of 16 is 86 in each group or 172 in total.

For the analysis of the surgical procedures on both primary outcome measures, at least 172 patients are needed. However, anticipating on a drop out rate of 10% we will include 172/0.9 or 192 patients (96 per group) in this trial.

Economic evaluation

The evaluation will include the direct medical costs, out-of-pocket expenses, and the indirect non-medical costs of production losses. The direct medical costs will include the costs of all diagnostic and therapeutic interventions, hospital admissions, specialist consultations and out-of-hospital care. Volume data will be gathered with clinical report forms, available hospital information systems, and the Health and Labour Questionnaire. Existing guidelines for health care costing research will be adhered to determine the relevant unit costs. Both the friction costs method as well as a human capital approach will be applied to derive the costs of lost productivity. After price-indexing all costs will be expressed in 2011 euros.

Time schedule

We plan an inclusion period of 12 months and a follow-up of 12 months. Cost-effectiveness analysis will take 3 months after completion of the data.

ProjectleadersJ.P.W.R. Roovers, MD, PhD

Dept. of Obstetrics and Gynaecology, AMC, Amsterdam, the Netherlands

R.P. Schellart, MD

Dept. of Obstetrics and Gynaecology, Kennemer Gasthuis, Haarlem, The Netherlands

MethodologyM.G.W. Dijkgraaf, PhD

Dept of Clinical Epidemiology and Biostatistics, AMC, Amsterdam, the Netherlands